#include <iostream>

using namespace std;

int count (int n)
{
    if (n == 1 || n == 2)
    {
        return 1;
    }
    else
        return count(n - 1) + count(n - 2);
}
int main()
{
    int n;
    cin >> n;
    cout << count(n) << endl;
}